As an automatic ice making machine automatically producing a large amount of ice blocks, a flow-down type automatic ice making machine is known, for example, in which a vertically installed ice making unit is provided with an evaporation tube that is led out of a refrigeration system, and ice making water is spray supplied to the ice making unit that is cooled by this evaporation tube to produce ice blocks, and in which, in deicing operation, ice blocks are separated from the ice making unit to fall down and release. This automatic ice making machine is equipped with an ice making water tank to store a required amount of ice making water and is configured to, in ice making operation, pump the ice making water in the ice making water tank with an ice making water pump to supply it to the ice making unit, and to collect ice making water failed to freeze into the ice making water tank and then send it again towards the ice making unit. As the ice making unit completes ice making to be shifted from ice making operation to deicing operation, deicing water is spray supplied to a back face of the ice making unit to promote melting a frozen face with ice blocks and also the deicing water is collected into the ice making water tank, and this is used as ice making water in ice making operation for the next time.
In general, by supplying water at normal temperature from an external water supply source during deicing operation as deicing water (ice making water), such an automatic ice making machine described above is designed to be shifted to ice making operation after storing ice making water to be used for ice making operation for one cycle in the ice making water tank. That is, the ice making water tank needs a capacity capable of storing at least an amount of ice making water for one cycle of ice making operation (hereinafter, referred to as a necessary amount of ice making water), which has been a factor causing upsizing of the ice making water tank. In addition, in deicing operation, a lot of ice making water is necessary to be supplied to the ice making water tank, so that it takes time to fill the ice making water tank with ice making water, which also has caused a problem of longer deicing operation time period.
With that, an automatic ice making machine is proposed in which an ice making water tank having a capacity less than the necessary amount of ice making water is employed and, in a case where ice making water in the ice making water tank is lacking during ice making operation, water at normal temperature is additionally supplied from an external water source to the ice making water tank via a water feeding means as makeup water. Specifically, a float switch is equipped in the ice making water tank, and when the float switch detects a lower limit water level of ice making water during ice making operation, supply of makeup water is started by the water feeding means. Then, when the float switch detects an upper limit water level of ice making water, the water feeding means is designed to stop the supply of makeup water. This avoids upsizing of the ice making water tank to allow the entire size of the ice making machine to be compact and also to reduce the deicing time period (refer to Patent Document 1).